Controlling under surface heating/cooling

ABSTRACT

The invention relates to controlling an under surface heating/cooling. During a heating mode, the room temperature is increased by increasing the flow of the liquid in a supply loop ( 3 ). If the set point has an increase that is greater than a pre-determined value, the supply temperature of the liquid is increased. During a cooling mode, the room temperature is decreased by increasing the flow of the liquid in the supply loop ( 3 ). Correspondingly, in response to a set-point change greater than a pre-determined value, the supply temperature of the liquid is temporarily decreased.

BACKGROUND OF THE INVENTION

The invention relates to a method of controlling an under surfaceheating in which a room is heated using a supply loop in which liquid iscirculated for heating the room, the method comprising increasing roomtemperature by increasing the flow of the liquid in the supply loop.

The invention further relates to a method of controlling an undersurface cooling in which room is cooled using a supply loop in whichliquid is circulated for cooling the room, the method comprisingdecreasing room temperature by increasing the flow of the liquid in thesupply loop.

Yet further the invention relates to a hydronic heating/cooling systemcomprising a main supply pipe, a main return pipe, at least one supplymanifold, at least one return manifold, heating loops from the supplymanifold to the return manifold, actuators for controlling the flow inthe heating loops arranged to the supply manifold and/or the returnmanifold and a control unit comprising means for controlling theactuators for controlling the flow of the liquid in the supply loop.

Yet further the invention relates to a software product of a controlsystem of a hydronic heating system in which liquid is led along a mainpipe to supply manifold and distributed in the manifold into heatingloops, the heating loops returning to a return manifold, at least one ofthe manifolds having actuators for controlling the flow in the heatingloops.

Yet further the invention relates to a software product of a controlsystem of a hydronic cooling system in which liquid is led along a mainpipe to a supply manifold and distributed in the manifold into heatingloops, the heating loops returning to a return manifold, and at leastone of the manifolds having actuators for controlling the flow in theheating loops.

Heating systems typically have different set temperatures over the dayor week. The energy loss from a heated body is proportional to theambient temperature difference. It is therefore possible to save energyby lowering the temperature of a room, for example, during the nightwhen the room is not occupied. In a hydronic under surface heatingsystem, when the temperature is raised back to comfort level, typicallythe flow of the supply loop is increased. An under floor heating systemis quite a slow system. Thus, typically quite a long time, for exampleseveral hours, is needed to raise the temperature from the lower valueto a comfort temperature. Further, the heat-up time depends on theenergy loss of the room which for its part depends on outsidetemperature. Different gain curves depending on outside temperaturecould be used for compensating the outside temperature. However, thiskind of compensation is extremely complicated for transitions betweendifferent temperatures.

The document JP 11 182 865 discloses a solution in which water is heatedby primary paths and floor is heated by secondary paths. Thermistorsdetect the heat on the primary and secondary paths and control water bycontrol valves. The first thermistor is set to a target temperatureduring rapid heating operation. After reaching switching temperature,rapid heating is stopped and the second thermistor is set to a secondtarget temperature. The document JP 57 077 837 discloses a controlsystem of floor heating. The feeding amount of a fuel to a boiler at thetime of initiation of heating is increased. The document JP 57 062 330discloses a control system for floor heater. At the start of heating, inorder to accelerate the rise of heating, the boiler is operated at alarge input and the maximum hot water temperature so as to raise thesurface temperature of the heater.

BRIEF DESCRIPTION OF THE INVENTION

The object of the invention is to provide a new method and arrangementfor controlling under surface heating/cooling.

The method of the invention relating to the under surface heating ischaracterized by, in response to a set-point change greater than apre-determined value, increasing temporarily the supply temperature ofthe liquid.

Further, the method of the invention relating to the under surfacecooling is characterized by, in response to a set-point change greaterthan a pre-determined value, decreasing temporarily the supplytemperature of the liquid.

The system of the invention is characterized in that the control unitcomprises means for temporarily increasing the supply temperature of theliquid in heating mode and means for temporarily decreasing the supplytemperature of the liquid in cooling mode in response to a set-pointchange greater than a pre-determined value.

The software product of the invention relating to the under surfaceheating is characterized in that the execution of the software producton a control unit of the control system is arranged to provide thefollowing operations of increasing room temperature by increasing theflow of the liquid in the supply loop and, in response to a set-pointchange greater than a pre-determined value increasing temporarily thesupply temperature of the liquid.

Further, the software product of the invention relating to the undersurface cooling is characterized in that the execution of the softwareproduct on a control unit of the control system is arranged to providethe following operations of decreasing room temperature by increasingthe flow of the liquid in the supply loop and in response to a set-pointchange greater than a pre-determined value decreasing temporarily thesupply temperature of the liquid.

In the invention, during a heating mode, room temperature is increasedby increasing the flow of the liquid in a supply loop. If the set pointhas an increase that is greater than a pre-determined value, the supplytemperature of the liquid is increased. Thus, a boost mode is activatedfor raising the temperature. This provides the advantage that the stepresponse of the room temperature is faster, i.e., the room temperatureis raised faster. By reducing the heat-up time, energy is saved, becausethe average room temperature could be decreased by fast transitions whenincreasing the temperature. The solution also provides improved comfort.

In an embodiment, the zones with the latest set-point changes areprioritized by the controller for a period of time or until the setpoints are reached. This further speeds up the raising of thetemperature in these zones whereby the heating of the other parts is notessentially disturbed.

In another embodiment, cold liquid is supplied to the loop in the laststage before reaching the new set point. This feature reduces orminimizes the overshoot and the heating ramp can also be steep close tothe set point. Thus, the heating time can be reduced and overshootminimized.

In a yet another embodiment, previous transitions and outsidetemperatures are analyzed and the transition ramps are optimized on thebasis of the analysis. This feature further increases the speed of thetransition and reduces overshoot.

BRIEF DESCRIPTION OF THE FIGURES

Some embodiments of the invention are described in greater detail in theattached drawing in which

FIG. 1 is a schematic of a hydronic heating/cooling system.

FIG. 2 shows schematically the temperature of a room, and

FIG. 3 shows schematically the temperature of supply liquid.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a hydronic heating/cooling system. In the system, liquid isled along a main supply pipe 1 to a supply manifold 2. The supplymanifold 2 distributes the liquid to several heating loops 3. Theheating loops 3 make the liquid to flow through the rooms or spaces tobe heated or cooled. If the system is used for heating, the liquid canbe warm water, for example. On the other hand, if the system is used forcooling the liquid flowing in the pipes is cool liquid that cools therooms or spaces.

The pipes forming the heating loops 3 return to a return manifold 4.From the return manifold 4, the liquid flows back again along a mainreturn pipe 5.

Actuators 6 are arranged to the return manifold 4. The actuators 6control the flow of the liquid in the loops 3.

A control unit 7 controls the operation of the actuators 6. Theactuators 6 can also be arranged to the supply manifold 2. Further,there can be actuators both in the supply manifold 2 and in the returnmanifold 4. Either one of the manifolds 2 and 4 can further comprisebalancing valves. The balancing valves can be manually operated, forexample.

The system can also comprise a circulation pump 8 and a connectionbetween the main supply pipe 1 and the main return pipe, the connectionbeing provided with a mixing valve 11. A separate circulation pump 8and/or a connection between the pipes 1 and 5 is, however, not alwaysnecessary.

The control unit 7 measures the temperature of the liquid by atemperature sensor 9. The outside temperature is also measured by atemperature sensor 10. The control unit 7 can control the temperature ofthe liquid in the main flow pipe 1, i.e., the supply temperature of theliquid, on the basis of the outside temperature, for example. Thecontrol unit 7 can control the temperature of the liquid in the mainflow pipe 1 by controlling the mixing valve 11, for example.

The control unit 7 can comprise a zone controller part that controls theactuators 6 and the circulation pump and a primary controller part whichcontrols the mixing valve 11, for example. In such a case, the zonecontroller part and the primary controller part are connected by a bus,for example.

The room thermostats 12 are positioned in the rooms to be heated. Thetemperature in the rooms is measured by the thermostats and theinformation is led to the control unit 7. The user can also adjust theset point of the temperature by the thermostats 12. The set points canalso be adjusted by another adjuster or by a programmed pattern.

A hydronic under floor heating system distributes the needed heating toeach room in the building by controlling the hot water flow through aheating loop or supply loop in the floor. Normally, one loop per room isused but sometimes a large room is split into two or more loops. Acontroller will act on the information from the room thermostat andaccordingly turn the water flow on or off in the floor loop.

The floor loop or heating loop piping is typically made of cross-linkedpolyethylene plastic pipes, for example. These pipes can be used indifferent types of floor constructions, i.e., both concrete and woodenfloors can be heated this way. It is essential that the insulation,under the pipes, in the floor construction is good to avoid the leakageof energy out downwards. The floor loop layout depends on the heatdemand for each room.

In a concrete floor, typically 20-mm pipes are used, the pipes beingusually attached to a re-enforcing net before the final concretecasting. The recommendation is that the top of the pipes should be 30 to90 mm below the concrete surface and the pipe loops should be placed ata 300-mm center distance. Concrete conducts heat well, so this layoutwill lead to an even distribution of energy and give an even temperatureon the floor surface. This building method using concrete and 20-mmpipes is an economical way of building a UFH (underfloor heating)system.

Due to the good thermal conduction in concrete, the loop can be fed withlow supply temperature, normally below 35 degrees Celsius.

The step response is quite slow due to the large mass of the floor,normally between 8 to 16 h depending on the floor thickness.

In wooden floors there are some different construction techniquesavailable and we can divide them into two main categories: floor loopsinside the floor construction or on top of the floor construction. It isto be noted that all UFH wood construction techniques use aluminumplates to distribute the heat from the pipes. This compensates for thepoor heat conduction in wood. Generally speaking, all “in floor”constructions use 20-mm pipes and the “on floor” technique uses 17-mmpipes that are mounted in pre-grooved floorboards. However, it isself-evident to a person skilled in the art that the diameter of thepipes can also be different and it is determined according to the needand/or requirements set by the system and/or environment.

Due to the poor thermal conduction in a wooden floor, the loops need ahigher supply temperature than a concrete floor, normally up to 40degrees Celsius.

The step response is quicker than for concrete, normally between 4 to 6h depending on the floor construction.

The previously mentioned systems are primarily installed when a house isbuilt. In addition to these, there are UFH systems for afterinstallation. This system focuses on a low building height and the easeof handling, and uses smaller pipe diameters, and the pipes are mountedin pre-grooved polystyrene floor panels. The supply temperature and stepresponse are quite similar to those of wooden constructions.

The stroke cycle of the actuator is preferably less than 120 seconds.The actuator can be a conventional mechanical piston valve. The actuatorcan also be, for example, a solenoid valve. When using a solenoid valve,the stroke time of the actuator can be very short. Thus, the stroke timeor operating time of the actuator can be for example in the range of 0.1to 120 seconds. Preferably actuators with fast operating time are used.Thus, the operating time of the actuators is preferably less than 10seconds.

In the control system, the term “pulse width” refers to the on time ofthe flow, i.e., the duty cycle. A minimum pulse width is preferred inorder to achieve efficient heating. However, the minimum pulse width ispreferably determined such that during the duty cycle the longest loopis also filled with supply water. The minimum pulse width means that thetime frame of the control is quite short, which means high frequency.Preferably, the time frame is shorter than ⅓ of the response time of thefloor in the room to be heated. The time frame may vary for examplebetween 5 and 60 minutes. In order to achieve the feature that the dutycycles start at different moments in different loops, the length of theoff-times between the duty cycles can be varied using a pattern orrandomly. The variation must naturally be carried out within certainlimits, such that the percentage of the duty cycles can be kept at adesired value. Another option is to vary the pulse width using a patternor randomly in a corresponding manner. Yet another option is to usedifferent time frames in different loops. For example, in one loop thetime frame can be 29 minutes, in a second loop the time frame can be 30minutes, and in third loop the time frame can be 31 minutes. Of coursesometimes the duty cycles start simultaneously in different loops, butusing at least one of the above-mentioned systems, the duty cycles startat different moments in most cases. Thus, the object is to prevent theduty cycles in different loops from running synchronously.

The percentage of the duty cycle means how long the on-state of the timeframe is. In other words, if the time frame is 10 minutes and thepercentage of the duty cycle is 10%, it means that the flow is on for 1minute and off for 9 minutes, if the percentage is 50 the flow is on for5 minutes and off for 5 minutes and if the percentage of the duty cycleis 90, the flow is on for 9 minutes and off for 1 minute off. If thetime frame is short enough, control can be considered continuous if thesystem is slow enough, i.e., the response time of the floor is long.

This specification refers to hydronic under surface heating/cooling. Insuch a system, liquid is supplied to supply loops for cooling/heating.The liquid can be for example water or any other suitable liquid medium.The liquid may comprise glycol, for example. Under surfaceheating/cooling means that the supply loops are installed under thefloor, for example. The supply loops can also be installed in any othersuitable structure. The loops may be installed in the wall or ceiling,for example.

In an embodiment an on/off control is combined with pulse widthmodulation per room. The pulse width depends on the response in theroom. At the startup the pulse width is preferably always 50%. The timeframe for the pulse width can be 30 minutes, for example. It isimportant to prevent the different channels/loops from runningsynchronously. Adding a random value of −30 to +30 seconds to the timeframe can prevent this. Another possibility is to have a slightlydifferent time frame for each channel/loop. It is enough if thedifference is 5 seconds, for example.

The maximum value for the pulse width is 25 minutes and the minimumvalue is 5 minutes. The resolution can be 1 minute, for example.Preferably, the pulse width modulation counter is reset the by a changeof a set point which prevents delays in the system.

A heating cycle is defined as the time between one heating request andthe next heating request.

Maximum and minimum room temperatures are monitored and saved during afull heating cycle.

The pulse width is adjusted at timeout, at heat-up modes or after aheating cycle.

The master timeout for pulse width adjustment can be for example 300minutes.

The control system comprises an appropriate means for performing thedesired functions. For example, a channel block calculates the controlsignal based on the set point, the room temperature and the energyrequired. The energy is pulse width modulated and the energy requirementis calculated by measuring the characteristics of the room temperatureover time.

One way to describe this is that it is a traditional on/off control withself-adjusting gain.

In an embodiment, the pulse width modulation output can be adjustedbetween 15 to 70% of the duty cycle. The start value is 50%. The maximumand minimum values during an on/off cycle are stored and evaluated andthe duty cycle is adjusted if needed.

The pulse width modulation timer is restarted if the set point increasesmore than 1 degree.

The curve A in FIG. 2 shows how the temperature in one room changes ifthe procedure described below is used during a heating mode. The new setpoint T_(set) is larger than a pre-determined value. The request toraise the temperature can come from a room thermostat 12 adjusted by theend-user, for example. The set-point change can be larger than 3degrees, for example. This activates the boost mode, which means thatthe supply temperature of the liquid is increased. For example, it isbeforehand determined that the new set point must be reached at sixo'clock in the morning. The moment when the set point must be reached isshown in FIG. 2 with reference sign t₃. In a conventional system therising of the temperature would follow curve B, which is shown with adash and dot line. Thus, in a conventional system the rising of thetemperature takes quite a long time from the moment t₀ to the moment t₃.

Now, however, the supply temperature of the liquid is increased and itis possible to start the heating period at the moment t₁. Thus, therising of the temperature in the room happens rather fast.

However, the rise of the ramp is steep, which means that an overshoot,which is denoted with a dash and dot line C in FIG. 2, easily occurs.This overshoot can be reduced or minimized by lowering the supplytemperature before the set point is reached.

FIG. 3 illustrates the supply temperature of the liquid during a heatingmode. The ripple in the curve illustrates that the control unit 7adjusts the supply temperature on the basis of the outside temperature.At the moment t₁ the supply temperature is increased by adjusting themixing valve 11, for example. At the moment t₂ the supply temperature islowered. Thus, after the moment t₂ cooler supply liquid is supplied. Theroom is not cooled but it is heated less between the moments t₂, and t₃than between the moments t₁ and t₂. If only the mixing valve 11 iscontrolled, the supply temperature lowers according to the curve shownby the broken line D. Thus, the supply temperature lowers quite slowly.This means that the room temperature would act according to the line Ein FIG. 2.

However, if the supply temperature is lowered faster than shown by thecurve in FIG. 3 with a solid line, it is possible to start lowering thetemperature at the moment t₂. The supply temperature of the liquid canbe cooled by opening temporarily at least some of the actuators 6 of theother loops 3, which are not boosted. If there have been no heat callsin these loops, these loops contain liquid having lower temperature thanthe liquid in the boosted loop. These loops need to be opened only for ashort time. If this time is less than 10 minutes, for example, this doesnot substantially raise the temperature in the rooms through which theseloops pass.

The supply temperature between the moments t₂ and t₃ can be lower thanthe normal supply temperature before boosting. At the moment t₃ thesupply temperature can be raised to a normal level.

During a cooling mode a corresponding procedure is used. It is, however,self-evident that then room temperature is decreased by increasing theflow of liquid in the supply loop and, in response to a set-point changegreater than a pre-determined value, decreasing temporarily the supplytemperature of the liquid. The overshoot is reduced by supplying warmerliquid to the loop before reaching the set point.

The control unit 7 can comprise a software product whose execution onthe control unit 7 is arranged to provide at least some of theabove-described operations. The software product can be loaded onto thecontrol unit 7 from a storage or memory medium, such as memory stick, amemory disc, a hard disc, a network server, or the like, the executionof which software product in the processor of the control unit or thelike produces operations described in this specification for controllinga hydronic heating/cooling system.

In some cases the features described in this application can be used assuch regardless of other features. The features described in thisapplication may also be combined as necessary to form variouscombinations.

The drawings and the related description are only intended to illustratethe idea of the invention. The invention may vary in detail within thescope of the claims.

1. A method of controlling an under surface heating in which a room isheated using a supply loop in which liquid is circulated for heating theroom, the method comprising increasing room temperature by increasingthe flow of the liquid in the supply loop, and in response to aset-point change greater than a pre-determined value, increasingtemporarily the supply temperature of the liquid.
 2. A method accordingto claim 1, comprising prioritizing by a controller zones with latestset-point changes for a period of time or until the set points arereached.
 3. A method according to claim 1, comprising supplying coolerliquid to the loop before reaching the set point for reducing overshoot.4. A method according to claim 3, wherein the cooler liquid is obtainedby opening temporarily at least some of the actuators of other loops. 5.A method according to claim 1, comprising analyzing previous transitionsand outside temperatures and optimizing transition ramps on the basis ofthe analysis.
 6. A method according to claim 1, comprising controllingthe flow of the liquid on and off such that during a duty cycle the flowis high and between the duty cycles the flow is off, whereby roomtemperature is controlled by controlling the percentage of the dutycycles.
 7. A method of controlling an under surface cooling in which aroom is cooled using a supply loop in which liquid is circulated forcooling the room, the method comprising decreasing room temperature byincreasing the flow of the liquid in the supply loop, and in response toa set-point change greater than a pre-determined value, decreasingtemporarily the supply temperature of the liquid.
 8. A method accordingto claim 7, comprising supplying warmer liquid to the loop beforereaching the set point for reducing overshoot.
 9. A hydronicheating/cooling system comprising a main supply pipe, a main returnpipe, at least one supply manifold, at least one return manifold,heating loops from the supply manifold to the return manifold, actuatorsfor controlling the flow in the heating loops arranged to the supplymanifold and/or the return manifold and a control unit including meansfor controlling the actuators for controlling the flow of the liquid inthe supply loop, means for temporarily increasing the supply temperatureof the liquid in heating mode and/or means for temporarily decreasingthe supply temperature of the liquid in cooling mode in response to aset-point change greater than a pre-determined value.
 10. A systemaccording to claim 9, wherein the control unit comprises means forcontrolling cooler liquid to be supplied to the loop before reaching theset point in heating mode and/or for controlling warmer liquid to besupplied to the loop before reaching set point in cooling mode forreducing overshoot.
 11. A system according claim 9, wherein that theactuators are arranged to control the flow in the heating loops on andoff such that during the duty cycle the flow is high and between theduty cycles the flow is off.
 12. A software product of a control systemof a hydronic heating system in which liquid is led along a main pipe tosupply manifold and distributed in the manifold into heating loops, theheating loops returning a return manifold, at least one of the manifoldshaving actuators for controlling the flow in the heating loops, whereinthe execution of the software product on a control unit of the controlsystem is arranged to provide the following operations of increasingroom temperature by increasing the flow of the liquid in the supply loopand, in response to a set-point change greater than a pre-determinedvalue increasing temporarily the supply temperature of the liquid.
 13. Asoftware product of a control system of a hydronic cooling system inwhich liquid is led along a main pipe to a supply manifold anddistributed in the manifold into heating loops, the heating loopsreturning to a return manifold, and at least one of the manifolds havingactuators for controlling the flow in the heating loops, wherein theexecution of the software product on a control unit of the controlsystem is arranged to provide the following operations of decreasingroom temperature by increasing the flow of the liquid in the supply loopand in response to a set-point change greater than a pre-determinedvalue decreasing temporarily the supply temperature of the liquid.
 14. Amethod according to claim 2, comprising supplying cooler liquid to theloop before reaching the set point for reducing overshoot.
 15. A systemaccording claim 10, wherein that the actuators are arranged to controlthe flow in the heating loops on and off such that during the duty cyclethe flow is high and between the duty cycles the flow is off.